I've not had a problem using the same PDF - Please remember not to select the Shrink (or Fit) to Page scaling option if you're using Acrobat - make sure you select page scaling as "None", as this will definitely reduce the image... maybe that's the problem?

Cheers,

Andy.

Just to confirm that the PDF is fine if you un-select Shrink To Fit. I attempted to etch this yesterday and the IC sockets matched up perfectly with the holes.

Unfortunately, as this was my first time with Press N Peel, I managed to mess it up, and not all of the design melted onto the copper - damn! Back to the drawing board...

I count 6 100k trimpots on this PCB. Could I substitute 50k for any(or all) of these trims without sacrificing tracking?

On the parts placement document, it looks like these are multi-turn trims. But I'm guessing on the odyssey these wre horizontal single turn trims, right?

I have multi-turn trims from Futurlec, but I don't think they work very well. Maybe it's just me, and because they have so many turns, but I can't ever hear much change when I adjust them in past projects.

Congratulations! Have you got any photos of the front panel? I'd be interested to see how you've laid it out.

ericcoleridge wrote:

How do we increase the signal of the Oddy VCO? Is there a resistor that can be replaced or something?

I've been trying to figure out how to do this, as well as centering the output around 0, but unfortunately I'm a bit out of my depth when it comes to these things! I've been reading up about DC offsets and amplification but I'm a bit lost when it comes to implementing. If anyone has any ideas then I'd be really grateful too!

How do we increase the signal of the Oddy VCO? Is there a resistor that can be replaced or something?

Hi Eric,

I think this is what you want. I've lifted this from Thomas Henry's Build a Better Music Synthesizer - it's from his CEM VCO design. He used it on the Triangle output (which is also 0-5v PP) to convert it to 10v PP centered around zero.

I haven't tested it, but in theory it should be fine.

BTW, I've just taken a look at the 4023 VCF PCB foil I posted... definitely the same version as I've used to build my own VCF's. I wish I could be more help - could you PM some high rez images of your board to me, I'll see what I can do.

I think this is what you want. I've lifted this from Thomas Henry's Build a Better Music Synthesizer - it's from his CEM VCO design. He used it on the Triangle output (which is also 0-5v PP) to convert it to 10v PP centered around zero.

BTW, I've just taken a look at the 4023 VCF PCB foil I posted... definitely the same version as I've used to build my own VCF's. I wish I could be more help - could you PM some high rez images of your board to me, I'll see what I can do.

I actually don't own a digtal camera, but as soon as I can borrow one, I'll take some pics and post them. Thanks for your help.

Congratulations! Have you got any photos of the front panel? I'd be interested to see how you've laid it out.

I've got two of these boards etched, ones finished, the other still needs some assembly...

One is gonna get put together with an Arp Axxe MKI PCB (minus the VCF daughterboard) that I picked up on e-bay for $50. I'm gonna add a S+H section, a Yu-Synth Arp 4072 VCF, a mixer, maybe some other odds and ends, and essentially made an Arp 2600 reproduction. I've got some of the panel layed out in FPD with 30mm sliders. I have an Arp Solus, and I'm thinking of this project as a portable modular companion piece to my portable Solus. Both should be around the same size, and fit into the same size cases.

My second Dual Oddy VCO is gonna be the core of a Buchla 259 Programmable Complex Waveform Generator reproduction. I have a panel in FPD ready. The oddy VCOs will get coupled with a Serge style 3900 Norton Amp VC Saw to Tri/Sine waveshaper, a VC X-fader for low harmonic (Sine) to high harmonic (square) cross fading, and an Ian Fritz wavefolder for extreme VC Timbre modulation. there's also a Modulation Index, and all the other 259 sections. I have most everything done already.

i'll definitely try to get pictures up of all these projects as they materialize.

If I wanted to use ferrite beads for power supply filtering would I just replace the 2 jumpers for the main + & - voltages or would I also use one on the tap off of the + voltage that goes to the trace that hits the VCO 2 Freq multi-turn trimmer?

If I wanted to use ferrite beads for power supply filtering would I just replace the 2 jumpers for the main + & - voltages or would I also use one on the tap off of the + voltage that goes to the trace that hits the VCO 2 Freq multi-turn trimmer?

That would be fine... You could increase the value of the two smoothing caps which would also help, but I've had no problems leaving everything as it is.

Still working on remainder of the modules - LFO, Noise, S&H coming up soon.

EDIT - I'm not so great with photo software and can't export from FPD, so I'm just attaching the FPD file.

Also, Andy, which VCO is synced to which - which is the master and which is the slave oscillator? I'm guessing what I'll call oscillator 2 is the "slave" osc, , the circuit beneath the power supply pads - that it's the one that resets to the other osc circuit to the left of the PCB image you posted.

One more question I can't quite figure out from the schematic and Andy's layout - which throw is the switch flipped to for sync to be active? As it is on Andy's diagram - http://electro-music.com/forum/phpbb-files/arp_odyssey_dual_vco_126.pdf - as he has that switch illustrated here, the switch right now is connected to the lower throw (which connects the pole of the switch to a jumper leading to a 100K resistor and then a 2N3904 transistor etc..., while the other "upper" throw is connected to the negative voltage rail through a 100K resistor). Which throw activates the sync connection? In the schematic the sync switch simply has an "off" throw which connects to the positive voltage, so this seems different than what I'm seeing on Andy's layout.

In the schematic the sync switch simply has an "off" throw which connects to the positive voltage, so this seems different than what I'm seeing on Andy's layout.

Thanks again.

The schematic above is for the Mk 1 VCO (although there's not much difference soundwise) my layout is from the Mk 2/3.

VCO 2 provides the sync signal, and as shown on my layout, sync occurs when the switch toggle is down. In the "up" position the sync input to VCO 1 is tied to -15v via a 100k resistor, which prevents any spurious re-triggering.

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